1. Field of the Invention
The present invention relates to novel polyamines useful as active ingredients in pharmaceutical compositions and therapeutic methods of treatment.
2. Description of the Prior Art
Because of the sustained increases in polyamine biosynthesis in pre-neoplastic and neoplastic tissues, a great deal of attention has been directed to the polyamine biosynthetic network as a target in anti-neoplastic strategies [Pegg, "Polyamine Metabolism and Its Importance in Neoplastic Growth and as a Target for Chemotherapy," Cancer Res., Vol. 48, pages 759-774 (1988); and Marton et al, "Directions for Polyamine Research," J. Cell Biochem., Vol. 45, pages 7-8 (1991)]. Initial work focused on the design and synthesis of compounds which would inhibit L-ornithine decarboxylase (ODC) [Bey et al, "Inhibition of Basic Amino Acid Decarboxylases Involved in Polyamine Biosynthesis," Inhibition of Metabolism Biological Significance and Basis for New Therapies, McCann et al, eds.; Academic Press: Orlando, Fla., pages 1-32 (1987)] and S-adenosyl-L-methionine decarboxylase (AdoMetDC) [Pegg, Cancer Res., Vol. 48, supra; and Williams-Ashman et al, "Methylgly-oxal Bis(guanylhydrazone) as a Potent Inhibitor of Mammalian and Yeast S-Adenosylmethionine Decarboxylases," Biochem. Biophys. Res. Commun., Vol. 46, pages 288-295 (1972)]. Some success was achieved through this approach in that difluoromethylornithine (DFMO), an ODC inhibitor, and methylglyoxylbis(guanylhydrazone) (MGBG), an AdoMetDC inhibitor, were effective against both in vivo and in vitro tumors [Sunkara et al, "Inhibitors of Polyamine Biosynthesis: Cellular and In Vivo Effects on Tumor Proliferation," Inhibition of Polyamine Metabolism Biological Significant Cause and Basis for New Therapies, McCann et al, eds.; Academic Press: Orlando, Fla., pages 121-140 (1987); and Pegg et al, "S-Adenosylmethionine Decarboxylase as an Enzyme Target for Therapy," Pharmacol. Ther., Vol. 56, pages 359-377 (1992)]. However, clinical trials did not mirror the success realized in the model systems; the drug either was too toxic as with MGBG [Pegg et al, Biochem. Pharmacol., Vol. 27, pages 1625-1629 (1978)] or was unable to show significant impact on tumors in humans as with DFMO [Schecter et al, "Clinical Aspects of Inhibition of Ornithine Decarboxylase with Emphasis on the Therapeutic Trials of Eflornithine (DFMO) in Cancer and Protozoan Diseases," Inhibition of Polyamine Metabolism. Biological Significance and Basis for New Therapies, McCann et al, eds.; Academic Press: Orlando, Fla., pages 345-364 (1987)]. One of the problems with the target enzymes ODC and AdoMetDC is associated [Seiler et al, "Polyamine Transport in Mammalian Cells," Int. J. Biochem., Vol. 22, pages 211-218 (1990)] with their very short half-lives, i.e., about 20 minutes. This can translate into a protracted exposure requirement for patients which is a less than desirable situation. Nonetheless, both DFMO and MGBG served well as proof of principle that the polyamine biosynthetic network was an excellent target in the design of anti-cancer drugs.
It would thus be desirable to design polyamine analogues which would be incorporated via the polyamine transport apparatus and, once in the cell, would find their way to the same subcellular distribution sites as the normal polyamines do, but would be unable to be further processed [Janne et al, "Polyamines in Rapid Growth and Cancer," Biochim. Biophys. Acta, Vol. 473, page 241 (1978); and Porter et al, "Enzyme Regulation as an Approach to Interference with Polyamine Biosynthesis--an Alternative to Enzyme Inhibition," Enzyme Regul., Vol. 27, pages 57-79 (1988)]. They would appear enough like the natural polyamines to shut down polyamine enzymes just as when the cells are exposed to exogenous spermine.
Thus, a series of terminally N-alkylated tetraamines, which exhibit anti-neoplastic activity against a number of murine and human tumor lines both in vitro and in vivo, were assembled [Bergeron et al, "Synthetic polyamine analogues as antineoplastics," J. Med. Chem., Vol. 31, pages 1183-1190 (1988); Bergeron et al, "Antiproliferative Properties of Polyamine Analogues: a Structure-Activity Study," J. Med. Chem., Vol. 37, pages 3464-3476 (1994); Bernacki et al, "Antitumor Activity of N,N'-Bis(ethyl)spermine Homologues Against Human MALME-3 Melanoma Xenografts," Cancer Res., Vol. 52, pages 2424-2430 (1992); Porter et al, "Biological Properties of N.sup.4 -Spermidine Derivatives and Their Potential in Anti-cancer Chemotherapy," Cancer Res., Vol. 42, pages 4072-4078 (1982); and Porter et al, "Biological Properties of N.sup.4 - and N.sup.1,N.sup.8 -Spermidine Derivatives in Cultured L1210 Leukemia Cells," Cancer Res., Vol. 45, pages 2050-2057 (1985)]. These tetraamines have been shown to utilize the polyamine transport apparatus for incorporation [Bergeron et al, J. Med. Chem., Vol. 37, supra; and Porter et al, "Aliphatic Chain Length Specific of the Polyamine Transport System in Ascites L1210 Leukemia Cells," Cancer Res., Vol. 44, pages 126-128 (1984)], deplete polyamine pools [Bergeron et al, "Role of the Methylene Backbone in the Antiproliferative Activity of Polyamine Analogues on L1210 Cells," Cancer Res., Vol. 49, pages 2959-2964 (1989)], drastically reduce the level of ODC [Pegg et al, "Control of Ornithine Decarboxylase Activity in .alpha.-Difluoromethylornithine-Resistant L1210 Cells by Polyamines and Synthetic Analogues," J. Biol. Chem., Vol. 263, pages 11008-11014 (1988); and Porter et al, "Relative Abilities of Bis(ethyl) Derivatives of Putrescine, Spermidine and Spermine to Regulate Polyamines Biosynthesis and Inhibit L1210 Leukemia Cell Growth," Cancer Res., Vol. 47, pages 2821-2825 (1987)] and AdoMetDC activities [Pegg et al, J. Biol. Chem., Vol. 263, supra; and Porter et al, Cancer Res., Vol. 47, supra] and in some cases to up-regulate spermidine/spermine/N.sup.1 -acetyltransferase (SSAT) [Pegg et al, "Effect of N.sup.1,N.sup.12 -Bis(ethyl)spermine and Related Compounds on Growth and Polyamine Acetylation, Content and Excretion in Human Colon Tumor Cell," J. Biol. Chem., Vol. 264, pages 11744-11749 (1989); Casero et al, "Differential Induction of Spermidine/Spermine N.sup.1 -Acetyltransferase in Human Lung Cancer Cells by the Bis(ethyl)polyamine Analogues," Cancer Res., Vol. 49, pages 3829-3833 (1989); Libby et al, "Major Increases in Spermidine/Spermine-N.sup.1 -Acetyltransferase by Spermine Analogues and Their Relationship to Polyamine Depletion and Growth Inhibition in L1210 Cells," Cancer Res., Vol. 49, pages 6226-6231 (1989); Libby et al, "Structure-Function Correlations of Polyamine Analog-Induced Increases in Spermidine/Spermine Acetyltransferases Activity," Biochem. Pharmacol., Vol. 38, pages 1435-1442 (1989); Porter et al, "Correlations Between Polyamine Analog-Induced Increases in Spermidine/Spermine N-Acetyltransferase Activity, Polyamine Pool Depletion and Growth Inhibition in Human Melanoma Cell Lines," Cancer Res., Vol. 51, pages 3715-3720 (1991); Fogel-Petrovic et al, "Polyamine and Polyamine Analog Regulation of Spermidine/Spermine N.sup.1 -Acetyltransferase in MALME-3M Human Melanoma Cells," J. Biol. Chem., Vol. 268, pages 19118-19125 (1993); and Shappell et al, "Regulation of Spermidine/Spermine N.sup.1 -Acetyltransferase by Intra-cellular Polyamine Pools-Evidence for a Functional Role in Polyamine Homeostasis," FEBS Lett., Vol. 321, pages 179-183 (1993)]. Interestingly, on incorporation of the tetraamine analogues, the total picoequivalents of charge associated with the analogues, as well as the natural polyamines, is maintained for about 24 hours. Thus, as the cell is incorporating n picoequivalents of drug, it is excreting n picoequivalents of natural polyamines.
Very small structural alterations in these spermine analogues and homologues result in substantial differences in their biological activity [Bergeron et al, Cancer Res., Vol. 49, supra]. For example, while the tetraamines N.sup.1,N.sup.12 -diethyl-spermine (DESPM), N.sup.1,N.sup.11 -diethylnorspermine (DENSPM) and N.sup.1,N.sup.14 -diethylhomospermine (DEHSPM) suppress ODC and AdoMetDC to about the same level at equimolar concentrations, the effect of both DESPM and DEHSPM on cell growth occurs earlier than that observed for DENSPM. The K.sub.i value of DENSPM is over 10 times as great [Bergeron et al, Cancer Res., Vol. 49, supra] as those of DESPM and DEHSPM for the polyamine transport system. However, the most notable difference between the three analogues is related to their ability to stimulate SSAT [Casero et al, Cancer Res., Vol. 49, supra; Libby et al, Cancer Res., Vol. 49, supra; Libby et al, Biochem. Pharmacol., Vol. 38, supra; and Porter et al, Cancer Res., Vol. 51, supra]. The tetraamine DENSPM up-regulates SSAT by 1200 fold in MALME-3 cells, while DESPM and DEHSPM stimulate SSAT by 250- and 30-fold, respectively [Porter et al, Cancer Res., Vol. 51, supra]. Thus, the impact of the tetraamine compounds on cell growth was shown to be dependent on: the distance between the nitrogens; the nature of the terminal alkyl substituents [Bergeron et al, J. Med. Chem., Vol. 37, supra] and, most importantly, on the charge status of the molecules [Bergeron et al, "The Role of Charge in Polyamine Analogue Recognition," J. Med. Chem., Vol. 38, pages 2278-2285 (1995)].
It was decided to establish whether or not a similar structure activity relationship exists for triamines, i.e., analogues of spermidine. The importance of this issue is underscored by the tremendous difference in toxicity between the triamines and tetraamines in general. Triamines are much less toxic, thus making them of potentially useful therapeutic value [Bergeron et al, "Metabolism and Pharmacokinetics of N.sup.1,N.sup.11 -Diethylnorspermine," Drug Metab. Dispos., Vol. 23, pages 1117-1125 (1995)].
It is, therefore, an object of the present invention to provide certain novel triamines possessing biological activity, in particular, anti-neoplastic activity.